A severely-ill man from the Middle East is being treated in a London hospital suffering from a mystery respiratory virus that has killed one patient in Saudi Arabia.

The 49-year-old is in intensive care after being transferred to the UK via air-ambulance from Qatar where he was taken ill a few weeks ago having recently visiting Riyadh.

The Health Protection Agency (HPA) said the infection is a new type of coronavirus different from any previously found in humans.

Sky's Health Correspondent Thomas Moore said: "He's being treated in isolation in hospital with barrier nursing where he's severely ill with renal failure and breathing problems and hospital staff are looking to make sure no-one else will come into contact with this virus."

Coronaviruses are responsible for illnesses such as the common cold but can also cause more severe infections, like Severe Acute Respiratory Syndrome (Sars).

Professor John Watson, from the HPA, said: "In light of the severity of the illness that has been identified in the two confirmed cases, immediate steps have been taken to ensure that people who have been in contact with the UK case have not been infected.

"Further information about these cases is being developed for healthcare workers in the UK, as well as advice to help maintain increased vigilance for this virus.

"This information is also being shared with national and international authorities including the World Health Organisation and the European Centre for Disease Control."

Between November 2002 and July 2003, an outbreak of the Sars coronavirus in Hong Kong spread to 37 countries, infecting 8,422 people, 916 of which later died.

The Saudi Ministry of Health announced at the weekend that the new virus had been diagnosed in two people, one of whom later died.

They added that coronaviruses are well known and most of those diagnosed with them recover with no complications after receiving treatment.

However, in some cases, infected patients develop complications affecting the respiratory system and the kidneys, which can cause death among elderly patients or those with respiratory and heart conditions.